1. Field of the Invention
The present invention concerns a method for planning an examination of an examination subject in a magnetic resonance system (MR system), of the type wherein the planning of the examination ensues based on a composite overview image that was assembled from at least two individual images. The present invention is, however, not exclusively for persons for whom a larger body region should be represented by MR images.
2. Description of the Prior Art
Imaging by means of magnetic resonance has increasingly proven to be indispensable for the diagnosis of various pathologies. In magnetic resonance systems used for such imaging, the trend has recently emerged that ever shorter magnet configurations are used for generation of the polarization (basic) field B0. These short magnet configurations help to reduce the claustrophobia that is typical for the examined person in closed magnet configurations since (dependent on the examined body part) the head projects out of such shorter magnets.
These shorter magnets, however, lead to the situation that the available field of view in the acquisition becomes ever smaller, such that it becomes more difficult to cover larger examination regions with only one examination (scan).
Furthermore, MR techniques have been developed with which a larger examination region can be examined, by the table on which the examined person rests being moved through the magnet, with MR images being acquired at successive table positions. The MR images acquired at the successive table positions are then assembled into an overall image.
Furthermore, an overview measurement typically ensues at the beginning in the examination, with the further progression of the examination being planned using the overview image by the position of the imaging slices and, if applicable, the parameters of the imaging being determined using the overview image. A number of overview measurements are conducted in the planning of an examination of a larger body region. The body regions to be examined, for example the head, abdomen and legs, are thereby measured in individual levels. After the end of the last level, the resulting images of the individual levels are combined. The image of the body thereby created is provided to the user for planning of the slices for the further measurements.
DE 103 46 410 A1 describes a method that enables a standardized description of the patient-related position and orientation of exposures in a magnetic resonance system, wherein a parameterized, anatomical body model is individualized by initial MR overview exposures of the patient, and patient-related information regarding the individualized model is determined from the relative position of the subsequent diagnostic slice image exposures for the position and orientation of the slice image exposures.
DE 103 57 203 A1 describes a method for representation of images in a magnetic resonance system, wherein an anatomical standard model is selected, the geometry of which is variable for an examination subject to be examined dependent on a diagnostic question. A number of overview images are subsequently acquired, and the image parameters are established dependent on the selected anatomical standard model.
According to the prior art, for a whole-body overview measurement, the image composition is activated only upon the ending of the measurement for the last level. The result images of the measurements of all individual levels are then assembled into a whole-body resulting image using an algorithm. The combined resulting images are provided to the user for planning the further examination. For planning an examination of a large body region, the user thus must wait until the last level is measured and the output image has been created. The user thus can begin the planning for measurements of the head level only when the overview measurement has been completely concluded and the resulting images of the overview images exist. This slows the entire examination and increases the time duration of the overall examination since the planning of the actual measurement can be begun only very late, which increases the cost of the examination.